1. Field of the Invention
This invention relates to an improved fluid flow sensing switch device and method of making the same as well as to a fuel control system utilizing such device for controlling the operation of electrical ignition means for a burner means of the fuel control system.
2. Prior Art Statement
It is known to applicant to provide in a fuel control system, a fluid flow sensing switch device having a housing means provided with a fluid flow passage therethrough defined by an inlet and an outlet separated by a valve seat controlled by a movable valve member that is operated by the pressure differential between the inlet and the outlet, the device having an electrical switch construction operatively associated with the valve member and having contact means thereof actuated by the pressure differential. A pressure regulator is provided for such system and is disposed intermediate such fluid flow sensing switch device and the burner means that receives fuel from the fluid flow sensing switch device.
For example, see the following co-pending U.S. Patent Application: (1) Ser. No. 936,112 filed Aug. 23, 1978.
The fluid flow sensing switch device of Item (1) above has one contact of the electrical switch construction carried by a flexible diaphragm that actuates the switch construction and the movement of the valve member by sensing the pressure differential between the inlet and the outlet across the same, and has the other contact of the switch construction carried on the valve member to be contacted by the diaphragm contact when the diaphragm moves its contact against the valve member contact so that the switch construction will be closed before the diaphragm can move the valve member to an open position thereof.
In the system of Item (1) above, such fluid flow sensing switch device is utilized in combination with a pressure regulator that is disposed intermediate the fluid flow sensing switch device and the burner means that receives fuel therefrom so that the fuel will be at a proper pressure valve when received by the burner means.
It was found according to the teachings of applicant's copending patent application, Ser. No. 936,113 filed Aug. 23, 1978, that the contact means of the electrical switch construction of Item (1) above can be arranged and comprise a pair of spaced apart contacts carried by the flexible diaphragm and a bridging contact member carried by the valve member and being adapted to make contact with the pair of contacts and thereby bridge the pair of contacts to close the switch construction.
It is also known to applicant to provide an electronic switching circuit to be controlled by the switch construction of such a fluid flow sensing switch device so that a relatively small current flow can be controlled by the switch construction of the fluid flow sensing switch device to eliminate any build up of carbon on the contacts thereof while permitting the electronic switching means to control a large current flow for operating the burner ignition means.
For example, see the following copending U.S. patent application: (2) Ser. No. 936,116, filed Aug. 23, 1978.